Variable scale counter



Oct, 14, 1958 R. A. coLA 2,856,558

VARIABLE SCALE: COUNTER Filed Feb. 2v, 195e fi `rREVERSE mpur +250 EVEN i @Elus A Lbf A `NaeA INBBA M Di-ES NES/2 31 35 30 25- 34. 2? B SPADE CURRENT l V93 i INVENTOR. RUDOLPH A, COLA Vgg BY 5 Vgl sPADE VOLTAGE Vg Vs W'wk United States Patent O VARIABLE SCALE COUNTER Rudolph A. Cola, Camden, N. J., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Application February 27, 1956, Serial No. 568,070

Claims. (Cl. 315-85) This invention relates to signal counting circuits and particularly relates to variable scale counting circuits useful for pulses occurring at random and at high recurrence rates.

To enable high speed counting, a multi-position electron beam switching tube is used, of the magnetron type described in the United States Patent No. 2,721,955 issued to Sin-pih Fan and Saul Kuchinsky on October 25, 1955. A magnetron beam switching tube of this type may comprise a cathode with a 4plurality of beam receiving compartments positioned concentrically in a circular row about the cathode. Each of the compartments comprises a spade electrode for locking the beam in position, a target electrode for receiving the beam, and a switching electrode for stepping the beam from one position to another. The spade electrodes are positioned concentrically about the cathode and spaced apart from each other to permit two adjacent spades to detine the side walls of a beam receiving compartment. The target electrodes are arranged concentrically about the spade electrodes and are positioned to individually ex tend across the spacings between adjacent ones of said spade electrodes to thereby receive substantially the entire beam passing into the compartment. The switching electrodes are arranged concentrically about the cathode and each switching electrode is individually positioned in a separate compartment in the vicinity of one of the two spade electrodes and the target electrode. A magnetic field is caused to permeate the tube with flux lines substantially parallel to the cathode and the electrodes. As well known in the art, this magnetic iield in conjunction with the electric iield set up between the cathode and spade electrodes will cause the electron beam to follow a path extending between two spades when all spades except one are at a high potential and the one s at about the cathode potential. As the beam enters the compartment adjacent to the low potential spade on the side from which electrons are coming, part of it will be received by the low potential spade and will develop an IR voltage drop in a series connected resistor to hold its potential at a low value and keep the beam locked in on the target electrode.

To provide switching of the beam to the next compartment, the switching electrode is so positioned as to alter the beam path so that the adjacent high potential spade receives beam current. This lowers the potential of the spade enough to cause the beam to step into the adjacent compartment. The beam normally progresses from one compartment to the next in that direction deiined by the polarity of the magnetic field. The electrons travel around the cathode in a direction determined fby the application of the right hand rule for interaction of current and magnetic iiux, and the beam advances in the upstream direction on this electron travel. By coupling the switching electrodes into two sets, each `including alternate electrodes, the electron beam can be `caused to advance from one compartment to the next by changing the potential of the to sets of switching electrodes alternately.

When a magnetron beam switching tube is used n a variable scale counter, two actions must occur in rapid sequence: the electron beam must be cut olf from the last beam receiving position which is used, and a beam must be reset on the initial position for a repetition of the beam switching cycle. p

An important object of this invention is to provide an improved variable scale counter using a magnetron beam switching tube with an automatic beam reset `circuit which operates only when the tube is in. magnetron cutoff condition and a beam clearing circuit. which is selectably connectable to any counting position of the tube.

Another important object of this invention is to provide an improved variable scale counter using a magnetron beam switching tube connected to an impedance network which holds one spade at beam forming potential relative to all other spades when the tube is in cutoli' condition, with an additional impedance member selectably connected to any one of said other spades to provide a beam clearing action to cut-off condition when the beam reaches the selected spade.

Reference is made to the drawing in which:

Fig. 1 is a partial schematic diagram of a variable counter circuit;

Fig. 2 is a detailed schematic diagram of a variable counter circuit; and

Fig. 3 is a current/voltage graph of spade electrode characteristics.

The basic circuits for automatic beam. `resetting when the magnetron is cut-oli? and for clearing a beam when it has advanced to a selected position is shown in Fig. 1. A supply voltage Es is applied to a resistance network which connects to the spades 22 and targets 21. One spade 22 is connected through a series resistor 24 to a voltage divider of resistors 30 and 31. These resistors 30 and 31 are connected from voltage supply Es to ground and resistor 24 connects at their mid point which is held at about 2/3 of Es.

The remaining spades 22 and all of the targets v21 are connected through their respective series resistors 24 and 25 to a common resistor 38 which in turn connects to voltage supply Es. All of these remaining spades additionally connect to contact points 50 a multiposition switch 49. Movable arm 47 can contact any one of contacts 50. Resistor 46 connects arm 47 to common lead 36.

When arm 47 connects to contact 50 for a particular spade, resistor 46 then is put in parallel with the resistor 24 connected to that spade. Resistors 24 are in the order of kilohms and when part of the beam strikes a spade enable a spade to hold the beam stably in position by developing an adequate IR voltage drop. However resistor 46 is in the order of 47 kilohms, and lowers the spade-to-lead 36 path to about 37 kilohms. The portion of beam current which flows through the spade is not able to develop an adequate IR voltage drop through this lower resistance, and a beam will clear or cut off when such a spade is reached. Thus, in Fig. 1, the beam `would cut ott when position 3 is reached.

When the tube 20 first is energized, it is in magnetron cut-oli and no beam current flows. In this condition all the electrodes connected to lead 36 are at voltage -j-ES. However, spade 22 is separately connected to voltage divider resistors 30 and 31 and is at about 2/ 3 of voltage +Es. This causes a large voltage difference between spade 22' and all other spades, which distorts the electric field in the cathode-to-spade space and causes a beam to form on the 0 position.

Once an electron beam forms, beam current Hows through a resistor 25 and resistor 38. Common resistor 3 38 is in the order of 12 kilohms, and beam current produces an IR drop through it of about 2/3 ES. This brings lead 36 down to about the potential of point 34, once a beam is formed. Thus the voltage supplied to resistors 24 and 24 are equal while a beam is formed.

This beam then is switched one position for every incoming pulse, by proper application of these pulses to grids 23, as will be described. When the position selected by arm 47 of switch 49 is reached, the beam clears or cuts olf as above described. With no beam on any target, lead 36 and the connected electrodes again rise to -l-ES while spade 22 remains at about 2/ 3 -l-Es and another beam forms on position.

In Fig. 2, an exploded and linearized magnetron beam switching tube is shown in a detailed schematic view. Targets 21, spades 22, and switching grids 23 are arranged in sets of one each to form beam receiving positions 0 to 9. All spades 22 have a series resistor 24, in the order of 150 kilohms. All targets 21 have a series resistor 25 in the order of 6 to 10 kilohms, Switching grids 23 are connected in common circuits of alternate grids, conveniently classied as even grids (0, 2, 4, 6 and 8) and odd grids (1, 3, 5, 7, and 9) corresponding to their respective beam receiving positions.

The initial spade 22', for the 0 position, has its series resistor 24 separately connected to a voltage divider portion of the impedance network which connects a voltage supply to the various electrodes of tube 20. Resistors 30, 31 and 32 are connected in series from a voltage supply -|-E, in the order of 125 to 200 volts, to ground. Voltage -I-E divides across these resistors proportionally to the resistance of each in ratio to the total resistance. Point 34 is at a voltage in the order of .85 volts when `-l-E is approximately 130. The initial spade is held at this voltage when no electron beam is held by it, and drops to a lower voltage when a beam is held in the "0 position, because part of the beam current flows to spade 22. This current through resistor 24 produces an IR drop which enables spade 22 to hold 4the beam stably.

All of the remaining spades and all of the targets are connected through their respective series resistors 24 and 25 to a common lead 36. Inductance 37 and resistor 38 connect common lead 36 to point 35, which is at a voltage in the order of 130 volts. When no beam exists, all these commonly connected spades and targets are at the potential of point 35, since there is no IR drop in the impedance network connecting them to point 35. When a beam is on any one of the targets, beam current will produce IR drops in the resistances of the connecting network. Resistor 38 has an ohmic value in the order of 12 kilohms, which produces an IR drop of about 45 volts, reducing lead V36 to about 85 volts which is normal operating voltage and allows normal beam holding `and switching. Inductance 37 is added to enhance the voltage drop when a beam is formed, causing the voltage to drop at a faster rate to the value determined by resistor 38. Resistor 39 and diode 40 are a network for critical damping, shunted across inductance 37 to prevent ringing.

Beam current is a function of the square of supply voltage -l-E, i. ye. J(-l-E2), and the IR voltage drop it causes will vary correspondingly. Thus, when supply +B is raised from minimum level, spade 22' will rise in potential more rapidly than does lead 36, due to this beam current. Diode 60 connects from lead 36 to point 34 and keeps lead 36 at the bias voltage of spade 22 so long as beam current is on, permitting wider variation in supply -l-E.

With no beam, and all spades except the initial spade 22 at 130 volts, and the initial spade 22' at only 85 volts, the electric eld in the cathode-to-spade space is distorted. This distorted eld causes a beam to form in ,the "0 position. This beam grazes spade 22 and strikes target 21. The small amount of beam current owing to spade 22 produces an IR drop in resistor 24 and enables it to hold the beam stably.

Once a beam is formed on the 0 position, input pulses on terminal 41 of iiip-flop driver 42 will produce switching signals on even and odd grids in alternate sequence so the beam steps from one position to the next. To insure starting on the even grids, so that the grid for 0 position receives the first negative-going switching signal, a reverse input is applied to terminal 43. When a beam is cut o, the IR voltage drop in resistor 38 disappears and the potential of lead 36 rises, applying a positive pulse of about 45 volts to terminal 43. This positive pulse is applied to the grid of tube 44, causing tube 44 to conduct. The resulting negative pulse on the plate of tube 44 is cross-connected to the grid of tube 45, producing a positive pulse on the plate of tube 45 which is in turn cross-connected to the grid of tube 44 where it continues the change caused by the initial positive pulse until tube 44 is driven to saturation plate current. This condition of ilip-op driver 42 is stable and insures that an input pulse on terminal 41 will start tube 45 conducting and begin cutting oi tube 44. Due to the crossconnections, this process continues until tube 45 is saturated, stabilizing in that condition. The result is a negative pulse on even grids, switching the beam from 0 to l position. The next input pulse reverses the above process and tube 44 becomes saturated, putting a negative pulse on odd grids and switching the beam from l to 2 position.

Multiposition switch 49 contacts spades 22 in a selective manner as described for Fig. l. Resistor 46 and inductance 48 connect from common lead 36 to arm 47. With arm 47 positioned as shown, resistor 24 connected to the spade for position 3 is shunted by resistor 46 and inductance 48. While reistor 24 is of an ohmic value which enables spade 22 to hold a beam stably, the parallel Value of resistors 24 and 46 is too low in ohmic value for stable beam holding and allows the connected spade to hold the beam only momentarily. Inductance 48 prolongs this holding period a small amount by retarding the current through resistor 46 and delaying the full eect of its shunting effect. This allows the distributed capacity of this spade to be charged as rapidly as the spade in any intermediate position.

Once the electron beam cuts oft" due to this unstable spade resistance, all the electrodes on common lead 36 rise in potential, to about volts. This voltage change leaves spade 22' at 85 volts, or at a potential difference of about 45 volts below the other spades. This voltage difference distorts the electric iield in the spade-to-cathode space and causes a new beam to form on the H0 position. Thus a reset action occurs automatically whenever the beam is cut off. Actuation of manual reset switch 33 accomplishes the same result in that it clears the beam and leaves the circuit ready for resetting a beam on the O position as described.

Fig. 3V shows the current/Voltage characteristics for spade electrodes under various conditions. The smaller j characteristic is the steady-state characteristic of a spade which is holding a beam and which is the only spade at a depressed voltage. From inspection it can be seen that the load line for a spade series resistor Rs intersects the j curve at three points: (1) at Vs and zero current which means the beam would be cut-off; (2) at point X which is on a negative-resistance slope of the j curve and hence unstable; and (3) at point Y which is on a positive-resistance slope of the j curve and stable. The spades voltage and current will stabilize at point Y.

When a beam switches to a succeeding position, the next (or j+1) spade which then holds the beam will have the j-l-l characteristic curve so long as the preceding spade which just released the beam remains at its depressed voltage of point Y. However this preceding spade will rise to voltage Vs, because it draws no current after it loses the beam, and a reverse charging current from the voltage supply will charge it up to Vs. As the potential of the j spade climbs from the voltage of `annalisa point Y to the voltage Vs, the i+1 characteristic curve for the succeeding spade collapses to the j characteristic. So long as the spade resistance of this succeeding spade also is Rs, stable holding is then reestablished on this next position.

If the succeeding position has a lower ohmic value Rc for its spade resistor, then collapse of the i+1 characteristic to the "j characteristic leaves no possible stable position for beam voltage and current since the "j characteristic has no intersection with load line except at cut-ofi on the zero current axis.

In any beam switching sequence, the beam switches over as the next switching grid is depressed in voltage. This voltage change lifts the tail of the next, or (j+1), spades characteristic until this characteristic clears the load line for its series connected resistor. Fig. 3 shows switching grid voltages Vgl, Vgz, etc. in their effect on the j+1 characteristic. With the operating bias of about volts for switching grids shown as Vgn, Vgl, is somewhat less in magnitude, Vgg is even less positive, and Vga is least positive; i. e., the voltage changes are negative-going. As has been described, a negative-going voltage is needed to switch the beam. However, this negative change must be enough to lift the tail of the j+1 characteristic clear of the load line.

When the j+1 spade has resistance Rs in series, grid Voltage Vgz would be adequate for switching. When the j+1 spade has resistance Rc in series, then the grid voltage must go to about Vgg for switching. At this grid voltage, the j+1 characteristic is raised and misses the Re load line except at point Z. The succeeding spa-de then will stabilize at point Z so long as the j-{ l characteristic is maintained. When the collapsing characteristic drops below the Rc load line, the beam clears or cuts olf.

Thus an automatic beam reset circuit and a selectable beam clearing circuit have been provided, for Variable counting of any number up to the number of targets in 1a reliable manner yet responsive to rapidly recurring pulses to a rate of 100,00() per second. The entire beam clearing and resetting on the initial or 0 position requires an interval of less than six microseconds. Further these beam clearing and beam resetting actions are performed with-out use of intervening tubes or transistors.

What is claimed is:

l. A variable scale counter comprising a voltage dividing network, impedance means having a plurality of separate branches and a common branch connected to said network, a voltage dropping resistor connected to said voltage dividing network, a magnetron beam switching tube having a cathode, an initial spade connected to said voltage dropping resistor, a plurality of spades connected to branches of said impedance means, a plurality of targets connected to branches of said impedance means, and ya plurality of switching grids, and a multiposition switch having a separate contact connected to each of said plurality of spades and a movable arm and including a series resistor selectably connected from said common branch of said impedance means to one of said plurality of spades.

2. A variable scale counter comprising a voltage dividing network, impedance means having a plurality of separate branches and a common branch connected to said network, a magnetron beam switching tube including an initial spade connected to said voltage dividing network, a plurality of spades connected to separate branches of 6 said impedance means and a plurality of targets connected to branches of said impedance means, and resistance switching means selectably connected from a separate branch of said impedance means to one of said plurality of spades.

3. A variable scale counter comprising a magnetron beam switching tube having a cathode, a plurality -of spade electrodes, a plurality of switching grid electrodes, and la plurality of target electrodes, rst impedance means connected to one spade electrode, second impedance means connected to the remaining spade electrodes to said tar- .get electrodes and to said rst impedance means, beam clearing means connected to said second impedance means and selectably connected to any one of said remaining spade electrodes to alter the electrical field between said cathode and said spade electrodes, and beam resetting means connected to said first impedance means and to said cathode and responsive to completion of the beam clearing action to produce a beam forming potential on said one spade electrode.

4. A variable scale counter comprising a voltage supply, voltage dividing means connected to said voltage supply, a resistor to a first point on said voltage dividing means, a resistor network connected to a second point on said voltage dividing means and having a plurality of branches, a magnetron beam switching tube having a plurality of spade electrodes with one spade electrode connected to said iirst resistor and the remaining spade electrodes connected to separate branches of said resistor network and a plurality of target electrodes connected to separate branches of said resistor network, and a multiposition switch having a separate contact connected to each of said remaining spade electrodes and a movable contact arm connected to a separate branch of said resistor network.

5. A variable scale counter as in claim 4 wherein said magnetron beam switching tube includes a plurality of beam switching grid electrodes in common connections of alternate grids, and including a flip-Hop pulse amplifier having a pair of plate electrodes connected to said common connections of alternate grids, a pair of control grids cross connected to said plate electrodes with one grid additionally connected to said resistor network and both grids connected to a common pulse input point.

6. A variable scale counter as in claim 4 including indicating means having an anode connected to a common point in said resistor network and a plurality of cathodes connected one to each of said target electrodes.

7. A variable counter comprising a multi-position electron beam tube having a plurality of beam holding positions with each position including a target electrode adapted to receive an electron beam, a spade electrode adapted to form and hold an electron beam on its associated target electrode, and a switching electrode adapted to switch an electron beam from one position to the next; a variable resistance means coupled to each spade electrode and having a range of resistance values such that each spade may be operated in both stable and unstable conditions; each spade being able to hold an electron beam in the stable condition and unable to hold an electron beam in the unstable condition; and means coupled to one of said spade electrodes for resetting an electron beam on the target associated with said one of said spade electrodes.

8. A variable counter comprising a multi-position electron beam tube having a plurality of beam holding positions with each position including a target electrode adapted to receive an electron beam, a spade electrode adapted to form and hold an` electron beam on its associated target electrode, and a switching electrode adapted to switch an electron beam from one position to the next; a resistance means connected to each spade electrode and of suiiicient magnitude torender each spade stable in operation; means adapted to be coupled to each spade to render each spade unstable in operation and unable to form and hold an electron beam; and means coupled to one of -said spade electrodes for resetting an electron beam on the target associated with said one of said spade electrodes.

9. A variable counter comprising a multi-position electron beam tube having a plurality of beam holding positions With each position including a target electrode adapted to receive an electron beam, a spade electrode adapted to form and hold an electron beam on its associated tar get electrode, and a switching electrode adapted to switch an electron beam from one position to the next; a rst resistance means connected to each spade electrode and of sufficient magnitude to render each spade stable in operation; means adapted to be coupled to each spade to change the magnitude of the iirst resistance means and thereby render each spade unstable in operation and unable to form and hold an electron beam; and means coupled to one of said spade electrodes for resetting an electron beam on the target associated with said one of said spade electrodes.

l0. A variable counter comprising a multi-position electron beam tube having a plurality of beam holding positions with each position including a target electrode adapted to receive an electron beam, a spade electrode adapted to form and hold an electron beam on its associated target electrode, and a switching electrode adapted to switch an electron beam from one position to the next; a rst resistance means connected to each spade electrode and of sulicient magnitude to render each spade stable in operation; second resistance means adapted to be coupled in parallel with said iirst resistance means to lower the magnitude of the resistance and to render each spade unstable in operation and unable to form and hold an electron beam; and means coupled to one of said spade electrodes for resetting an electron beam on the target associated with said one of said spade electrodes.

References Cited in the file of this patent UNlTED STATES PATENTS Rajchman June 26, 1951 2,563,807 Alfven Aug. 14, 1951 2,591,997 Backmark Apr. 8, 1952 r i l 

